To obtain an on-vehicle device for an automatic toll collection system to which a card for the automatic toll collection system does not have to be inserted separately and which improves convenience because a 1st portable machine (portable machine having an engine function) can surely be carried out from the vehicle in the case of leaving the vehicle, theft prevention property can be improved and the engine can also be started by the 1st portable machine in the case of driving the vehicle (getting into the vehicle) by making the 1st portable machine starting the engine of the vehicle store 1st credit identification information for the automatic toll collection system and executing automatic toll collection according to the 1st credit identification information.

This on-vehicle device A for an automatic toll collection system which performs transmission and reception with a roadside device installed at a toll road and executes toll collection stores 1st credit identification information in a 1st portable machine 12 starting the engine of a vehicle and executes automatic toll collection according to the 1st credit identification information.